Field of the Technology
The invention relates to the field of cell sorting and analysis of microscopic biological entities. More particularly, the invention relates to the magnetic separation of microscopic biological entities and then the subsequent analysis of such separated entities, namely, CPC B03C 1/0332, 1/288, 1/035, 1/0335, 2201/18; C12N 13/00; G01N 15/1459, 2015/149, 2015/1006.
Brief Description of the Field
Antibodies are proteins that bind to specific antigens. An antigen is a specific molecule that could be present on a cell membrane, an organelle, a particular protein, etc. The antibody-antigen interaction is similar to that of a lock and key, in that there is usually only one, or very few, antigens that will bind to a specific antibody. This makes antibodies an excellent tool for identifying and labeling biological species of study.
For example, in a particular population of cells, some portion of cells may express a particular antigen that the others do not. Using a florescent antibody that binds to that particular antigen, one could incubate the population of cells with this antibody, which would bind only to the cells which expressed that particular antigen. After washing away the excess antibody, those cells expressing the antigen and thus being bound to florescent antibodies would fluoresce, while those cells not expressing the antigen would not fluoresce.
Antibodies are an extremely powerful tool for biological research, medical diagnosis, disease therapy, etc. There are hundreds of companies who manufacture and sell antibodies and there are hundreds of thousands of different antibodies that are commercially available. For example, Abnova Corporation manufactures and sells more than 50,000 antibodies.
Antibodies can be made to be magnetic. Antibodies can be coated with magnetic nanoparticles or can have such particles incorporated into them. These antibodies are then susceptible to magnetic forces. Consequently, whatever the antibody binds to will likewise be susceptible to magnetic forces. For example, after magnetic antibodies bind to a cell expressing their reciprocal antigen, that cell could be pushed or pulled by magnetic forces which are acting upon the antibodies. Because the attached antibodies are susceptible to magnetic forces, the entire cell could be pulled towards a magnetic field.
Cell sorting techniques using magnetic antibodies to sort cells are often called “Magnetic-activated cell sorting”, or MACS. A typical MACS procedure would involve first incubating a sample with magnetic antibodies. Cells expressing this antigen then attach to the magnetic antibodies. Afterwards the cell solution is transferred to a column inside of a strong magnetic field. Cells attached to magnetic antibodies (expressing the antigen) are retained in the column, while other cells (not expressing the antigen) flow through and out of the column.
The MACS method described in the preceding paragraph could be used positively or negatively with respect to the particular antigen(s). In positive selection, the cells expressing the antigen(s) of interest are retained in the column and can then be isolated after removing the magnetic field. Positive selection is useful for isolating a particular cell type. In negative selection, the magnetic antibodies are used against surface antigen(s) which are known to be present on cells that are not of interest. After incubating the sample with the magnetic antibodies and running the sample through the column, the cells that are not of interest are retained in the column and can be discarded, while the cells of interest are washed through the column into a separate vessel for further study.
There are many other applications and methods for MACS and they are often combined with other cell sorting techniques such as flow cytometry. There are likewise many manufactures of magnetic antibodies, e.g. Milteny Biotec, Thermo Fisher, etc.